Week 12

Question 1

Appreciate that AES is a block cipher with 128-bit blocks, and keys of length 128, 192 or 256 bits

Question 2

Appreciate that AES is an example of a substitution-permutation network that makes use of several rounds of operations that involve adding a round key, performing a substitution operation on the elements of the state, and permuting the elements of the state

Question 3

Appreciate that designing secure block ciphers is hard and should be left to the experts!

Question 4

Recognise that block cipher modes of operation are used for encrypting messages that are more than one block long

Question 5

Describe the ECB, CBC and CTR modes of operation

Question 6

Given an example of a block cipher, carry out encryption and decryption using the ECB, CBC and CTR modes of operation

Question 7

Discuss advantages and disadvantages of the ECB, CBC and CTR modes of operation